2017 Sales
Initial Model
For an initial pass, we constructed a model in which valid sales prices were predicted by land and improvement values. The values taken from this baseline model were then used to calculate updated assessed values.
Base Results
| COD |
12.986829 |
| Ratio |
1.008983 |
With a very basic model, we were able to achieve reasonable values on both COD and Ratio.
Existing Neighborhood Results
As a next step, we computed individual regressions for each pre-existing neighborhood with at least 5 sales.
Min = 5
Neighborhood Results
| trueCOD |
12.3640145 |
| ratio |
0.9852967 |
| proportion |
0.9108841 |
Min = 3
Neighborhood Results
| trueCOD |
11.6518168 |
| ratio |
0.9958052 |
| proportion |
0.9108841 |
New Neighborhoods (Individual Distance)
Min = 5
Neighborhood Results
| trueCOD |
12.1791030 |
| ratio |
0.9953730 |
| proportion |
0.9704129 |
Min = 3
Neighborhood Results
| trueCOD |
11.6267601 |
| ratio |
1.0029825 |
| proportion |
0.9704129 |
New Neighborhoods (Midpoint Distance)
Min = 5
Neighborhood Results
| trueCOD |
11.9493777 |
| ratio |
0.9956412 |
| proportion |
0.9682592 |
Min = 3
Neighborhood Results
| trueCOD |
11.4635032 |
| ratio |
1.0026736 |
| proportion |
0.9682592 |
School Districts
Min = 5
School District Results
| trueCOD |
12.966301 |
| ratio |
1.004886 |
| proportion |
1.000000 |
Min = 3
School District Results
| trueCOD |
12.966301 |
| ratio |
1.004886 |
| proportion |
1.000000 |
Tax Districts
Min = 5
Tax District Results
| trueCOD |
13.529929 |
| ratio |
1.021243 |
| proportion |
1.000000 |
Min = 3
Tax District Results
| trueCOD |
13.49978 |
| ratio |
1.02146 |
| proportion |
1.00000 |
Township
Min = 5
Township Results
| trueCOD |
13.657369 |
| ratio |
1.020274 |
| proportion |
1.000000 |
Min = 3
Township Results
| trueCOD |
13.657369 |
| ratio |
1.020274 |
| proportion |
1.000000 |
Tract
In an attempt to find an additional way to create neighborhoods, we also used Census Tracts.
Min = 5
Tract Results
| trueCOD |
13.0724675 |
| ratio |
0.9954585 |
| proportion |
0.9884304 |
Min = 3
Tract Results
| trueCOD |
13.0194347 |
| ratio |
0.9960852 |
| proportion |
0.9884304 |
Combined
After examining individual geographical areas, we made an effort to nest geographical features into two levels.
School District & Township
School District & Township Results
| trueCOD |
13.618109 |
| ratio |
1.019515 |
| proportion |
1.000000 |
Township & Tax District
Township & Tax District Results
| trueCOD |
13.529929 |
| ratio |
1.021243 |
| proportion |
1.000000 |
Tax District & Tract
Tax District & Tract Results
| trueCOD |
12.9042242 |
| ratio |
1.0035928 |
| proportion |
0.9342727 |
Clustering
Given the relative performance of tract, an effort was made to break the homes within tract into discreet clusters. The features selected clustering were acreage, year built, finished dwelling area and finished rooms. For each individual school district or tract, 2 distinct clusters were created.
School District Clusters
School District Cluster Results
| trueCOD |
13.001373 |
| ratio |
1.004109 |
| proportion |
0.993250 |
Tract Clusters
Tract Cluster Results
| trueCOD |
12.2761470 |
| ratio |
1.0036373 |
| proportion |
0.8031071 |
Mixed Models
Instead of fitting models to individual groupings, we also tried a mixed model in which every tract X cluster combination has its own slope within the model.
Base Results
| COD |
10.597028 |
| Ratio |
1.009745 |
Previous Years
Given the reasonable results of the tract X cluster combination, we can see how it performs over the previous years.
2016
Township Results
| trueCOD |
14.359149 |
| ratio |
1.041651 |
| proportion |
1.000000 |
Neighborhood Results
| trueCOD |
12.4446684 |
| ratio |
0.9859240 |
| proportion |
0.9678307 |
Tract Results
| trueCOD |
12.6581642 |
| ratio |
1.0021349 |
| proportion |
0.7999526 |
2015
Township Results
| trueCOD |
12.875449 |
| ratio |
1.018672 |
| proportion |
1.000000 |
Neighborhood Results
| trueCOD |
12.0115865 |
| ratio |
0.9807339 |
| proportion |
0.9226224 |
Tract Results
| trueCOD |
12.2462482 |
| ratio |
1.0006408 |
| proportion |
0.8021374 |
2014
Township Results
| trueCOD |
12.10949 |
| ratio |
1.02665 |
| proportion |
1.00000 |
Neighborhood Results
| trueCOD |
10.9318154 |
| ratio |
0.9910232 |
| proportion |
0.9628340 |
Tract Results
| trueCOD |
10.7454565 |
| ratio |
1.0012982 |
| proportion |
0.7861609 |
2013
Township Results
| trueCOD |
16.805726 |
| ratio |
1.028595 |
| proportion |
1.000000 |
Neighborhood Results
| trueCOD |
13.7349915 |
| ratio |
0.9935612 |
| proportion |
0.9634921 |
Tract Results
| trueCOD |
14.1780947 |
| ratio |
0.9991709 |
| proportion |
0.7949596 |
